排序方式: 共有53条查询结果,搜索用时 609 毫秒
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Bashir A. Mansoori Edward W. Dyer Christopher M. Lock Kevin Bateman Robert K. Boyd Bruce A. Thomson 《Journal of the American Society for Mass Spectrometry》1998,9(8):775-788
The effect on triple-quadrupole performance of applying an axial field, in an rf-only quadrupole collision cell operated at pressures sufficiently high that collisional focusing is operating, has been investigated. The advantages of such cells have been shown previously to include increased transmission and much improved resolution in fragment ion spectra relative to the performance of collision cells operating at lower gas pressures. The disadvantages of high-pressure collision cells all derive from the relatively long transit times for the ions, which can be long relative to characteristic times for scanning the first mass filter (precursor ion selector) or for switching its setting in multiple reaction monitoring (MRM) cycles. The present work describes experiments on a high-pressure cell in which an axial field is created through use of conical rather than cylindrical or hyperbolic rods. In addition, results of computations of the electric fields within such a cell, and of ion trajectories through it, are presented. It is shown that application of axial fields of the order of 0. 1 V/cm can remove all hysteresis effects associated with the long ion transit times, and thus provide excellent performance in quantitation work using MRM, as well as in other scan modes. Furthermore, the advantages of collisional focusing in quadrupole collision cells are shown to be unimpaired by these low axial fields. 相似文献
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Mohammad Reza Zamanloo Golamhassan Imanzadeh Yagoub Mansoori Mohammad Hassan Karimi 《Polymer Science Series B》2011,53(5-6):267-277
2,6-Bis-(2,5-dioxo-tetrahydro-N-(4-carboxyphenyl)pyrrol-3-yl)-pyrrolo[3,4-f]isoindole-1,3,5,7-teraone, a chiral diacid, was prepared from pyromellitic anhydride and L-aspartic acid in a three steps reaction pathway. The polycondensation reactions of the monomer with aromatic diamines were carried out in direct condensation reaction conditions. The synthesized poly(amide-imide)s had inherent viscosities in the range of 0.30–0.80 dl/g. Identification of all of the products were performed by conventional analytical techniques such as TLC, IR and 1H NMR/13C MR spectroscopy. Thermoanalytical techniques (TGA/DSC) showed useful levels of thermal stability, associated with relatively high glass transition temperatures and carbonized residues in excess of 40% at 600°C for the synthesized polymers. Amorphous morphology was obtained based on XRD patterns and DSC traces. The polymers were soluble in a variety of polar organic solvents and afforded transparent and relatively flexible to brittle films by solution casting. 相似文献
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Gholamhassan Imanzadeh Zahra Soltanizadeh Ali Khodayari Mohammadreza Zamanloo Yagoub Mansoori Jaber Salehzadeh 《中国化学》2012,30(4):891-899
An efficient and simple procedure for the synthesis of novel isatin derivatives is described. Michael addition of aniline Schiff bases of isatin or p‐toluidine Schiff bases of isatin to fumaric esters affords the Michael adduct compounds in good to high yields in the presence of K2CO3 and tetrabutylammonium bromide (TBAB) under solvent‐free conditions. Repeating of this reaction about spiro[1,3‐dioxolane‐2,3′‐indol]‐2′(1′H)‐one, as a Michael donor, in the presence of 1,4‐diazabicyclo[2.2.2]octane (DABCO) gives Michael adducts in remarkable yields under the same conditions. 相似文献
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The aza-Michael addition of 1,2,3,6-tetrahydrophthalimide with symmetrical fumaric esters has been performed efficiently in a solvent-free system at 100 °C and using 1,4-diazabicyclo[2.2.2]octane (DABCO) as a base in the presence of tetrabutylammonium bromide (TBAB). The products were obtained in good to high yields within 2.5-7.0 h. This reaction worked well on linear alkyl fumarates and was not effective with nonlinear alkyl fumarates. Although the reaction was also applicable to acrylates such as n-butyl acrylate, methacrylates and crotonates were not suitable Michael acceptors for this reaction. 相似文献
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Nitesh Singh Aadil Mansoori Gitanjali Jiwani Amolkumar U. Solanke Tarun K. Thakur Rakesh Kumar Mona Chaurasiya Anirudh Kumar 《Arabian Journal of Chemistry》2021,14(7):103243
Plant extracts are one of the best possible sources of bioactive molecules, and are being used globally as an antioxidants and natural antimicrobial compounds. In current study, Schefflera vinosa leaves extract was prepared through Soxhlet extraction procedure using methanol and chloroform as solvents. The extract was investigated for total antioxidant, phenolic and flavonoid contents, free radical scavenging and antimicrobial activities. The free radical scavenging activities were evaluated through 2,2- diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis-3-ethylbenzotiazolin-6-sulfonic acid (ABTS) and Ferric-reducing/ antioxidant power (FRAP) assay. The antimicrobial activity of extract was determined through poisoned food method. The methanolic extract has exhibited high antioxidant, phenolic, and flavonoid activities compared to chloroform extract. Similarly, free radical scavenging activities (ABTS, DPPH and FRAP) were higher in methanolic extract. Further, Fourier-Transform Infrared Spectroscopy (FTIR) used to determine the functional group and Gas chromatography-mass spectrometry (GC–MS) to elucidate volatile composition of the crude extract. Different functional group like N-H, O-H, C-O, C-N, C-H, C=O, C≡C and C-O-H presence indicate the existence of many metabolites in the extracts. GC–MS study identified 61 compounds and subsequently, these molecules were screened virtually using DockThor. Furthermore, antimicrobial study was confirmed against rice pathogens like Magnaporthe oryzae (M. oryzae) and Xanthomonas oryzae pv. oryzae (Xoo). Molecular docking study further suggested that phytomolecules (3-Isopropoxy-1,1,1,7,7,7-hexamethyl-3,5,5-tris (trimethylsiloxy) tetrasiloxane, and 2-Methoxy-5-methylthiophene) targets Histone Deacetylase (HDAC) of M. oryzae and Peptide Deformylase (PDF) of Xoo, which could inhibit their growth. Hence, this study indicated that Schefflera vinosa extracts could be an important ingredient as an antioxidant as well as antimicrobial agent against rice pathogens. 相似文献
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Magnetic mesoporous silica was prepared via embedding magnetite nanoparticles between channels of mesoporous silica (SBA‐15). The prepared composite (Fe3O4@SiO2‐SBA) was then reacted with 3‐chloropropyltriethoxysilane, sodium imidazolide and 2‐bromopyridine to give 3‐(pyridin‐2‐yl)‐1H‐imidazol‐3‐iumpropyl‐functionalized Fe3O4@SiO2‐SBA as a supported pincer ligand for Pd(II). The functionalized magnetic mesoporous silica was further reacted with [PdCl2(SMe2)2] to produce a supported N‐heterocyclic carbene–Pd(II) complex. The obtained catalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, vibrating sample magnetometry, Brunauer–Emmett–Teller surface area measurement and X‐ray diffraction. The amount of the loaded complex was 80.3 mg g?1, as calculated through thermogravimetric analysis. The formation of the ordered mesoporous structure of SBA‐15 was confirmed using low‐angle X‐ray diffraction and transmission electron microscopy. Also, X‐ray photoelectron spectroscopy confirmed the presence of the Pd(II) complex on the magnetic support. The prepared magnetic catalyst was then effectively used in the coupling reaction of olefins with aryl halides, i.e. the Heck reaction, in the presence of a base. The reaction parameters, such as solvent, base, temperature, amount of catalyst and reactant ratio, were optimized by choosing the coupling reaction of 1‐bromonaphthalene and styrene as a model Heck reaction. N‐Methylpyrrolidone as solvent, 0.25 mol% catalyst, K2CO3 as base, reaction temperature of 120°C and ultrasonication of the catalyst for 10 min before use provided the best conditions for the Heck cross‐coupling reaction. The best results were observed for aryl bromides and iodides while aryl chlorides were found to be less reactive. The catalyst exhibited noticeable stability and reusability. 相似文献
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Yagoub Mansoori Raana Sarvari Mohammad Reza Zamanloo Gholam Hassan Imanzadeh 《高分子科学》2010,28(1):21-28
<正>In the present work,new thermally stable polymers containing 1,3,4-oxadiazole units have been synthesized through Huisgen reaction of the aromatic bis-tetrazole compounds with the aromatic/aliphatic bis-acid chlorides in pyridine as solvent.The obtained polymers are insoluble or slightly soluble in polar aprotic solvents such as DMSO and DMF. Thermal analyses of the polymers using DSC and TGA techniques showed that the polymers had improved thermal stabilities.The model reaction was also investigated and the resulting bis-l,3,4-oxadiazole compounds were characterized by conventional spectroscopic methods. 相似文献